Which statement accurately describes catalysts?

Which statement accurately describes catalysts?

• A. They are substances that speed up a reaction without being consumed in the process
• B. They are substances that speed up a reaction by changing the temperature
• C. They are consumed in the reaction and change the equilibrium
• D. They act as reactants in the overall reaction

Answer: (A)

Catalysts speed up a reaction by providing an alternate pathway with lower activation energy, and they are not consumed in the process. Because they lower the energy barrier rather than adding heat, they increase how often reactant molecules reach the transition state, speeding the rate. They don’t change the temperature of the system themselves, and they don’t alter the final amounts of reactants and products—only the rate at which equilibrium is reached. In fact, they accelerate both the forward and reverse reactions equally, so the equilibrium composition remains unchanged. They may participate in mechanism steps, but they are regenerated and do not appear in the net equation. That’s why the best description is a substance that speeds up a reaction without being consumed.

Catalysts speed up a reaction by providing an alternate pathway with lower activation energy, and they are not consumed in the process. Because they lower the energy barrier rather than adding heat, they increase how often reactant molecules reach the transition state, speeding the rate. They don’t change the temperature of the system themselves, and they don’t alter the final amounts of reactants and products—only the rate at which equilibrium is reached. In fact, they accelerate both the forward and reverse reactions equally, so the equilibrium composition remains unchanged. They may participate in mechanism steps, but they are regenerated and do not appear in the net equation. That’s why the best description is a substance that speeds up a reaction without being consumed.